Energy changes questions

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Energy changes question collection

Review Energy changes questions for Chemistry, with correct answers shown and coverage across exothermic and endothermic reactions; reaction profile diagrams; activation energy.

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Question 1

An exothermic reaction transfers energy?
  1. To the surroundings
  2. From the surroundings
  3. To catalysts
  4. To reactants

Question 2

An endothermic reaction transfers energy?
  1. From the surroundings
  2. To the surroundings
  3. As light to the room
  4. Into products with no surroundings effect

Question 3

Where are products shown on an exothermic reaction profile?
  1. Below the reactants
  2. Above the reactants
  3. Level with the reactants
  4. At the activation-energy peak

Question 4

What is activation energy?
  1. Minimum energy needed for a successful reaction
  2. The total energy released by products
  3. The energy stored only in catalysts
  4. The energy needed to cool reactants

Question 5

How does a catalyst speed up a reaction?
  1. By providing an alternative pathway with lower activation energy
  2. By increasing the overall energy change, ΔH
  3. By being used up to release heat
  4. By increasing reactant mass

Question 6

Breaking chemical bonds requires?
  1. An input of energy
  2. Release of energy
  3. No energy change
  4. A change in pH

Question 7

What happens to energy when chemical bonds form?
  1. It is released
  2. It is absorbed
  3. It is unchanged
  4. It becomes activation energy

Question 8

In a bond energy calculation, which expression gives the overall energy change?
  1. Energy used to break bonds - energy released making bonds
  2. Energy released making bonds - energy used to break bonds
  3. Energy used to break bonds + energy released making bonds
  4. Energy released making bonds / energy used to break bonds

Question 9

If bond-making releases more energy than bond-breaking absorbs, what type of reaction is it?
  1. Exothermic
  2. Endothermic
  3. Thermal decomposition
  4. Reversible reaction

Question 10

Which equation is used in simple calorimetry?
  1. q = mcΔT
  2. q = mΔT / c
  3. q = cΔT / m
  4. q = mc / ΔT

Question 11

\(100\,\mathrm{g}\) of water is heated by \(5\,\mathrm{^\circ C}\). Use \(c = 4.2\,\mathrm{J\,g^{-1}\,^\circ C^{-1}}\). What is \(q\)?
  1. \(2100\,\mathrm{J}\)
  2. \(840\,\mathrm{J}\)
  3. \(21000\,\mathrm{J}\)
  4. \(500\,\mathrm{J}\)

Question 12

Which reaction type is usually exothermic?
  1. Neutralisation of an acid and an alkali
  2. Thermal decomposition
  3. Photosynthesis
  4. Electrolysis of molten salts

Question 13

Which process is usually endothermic?
  1. Thermal decomposition of calcium carbonate
  2. Combustion of methane
  3. Respiration
  4. Condensation of steam

Question 14

A chemical cell produces electricity from what type of reaction?
  1. A redox reaction between different materials
  2. Thermal decomposition
  3. Acid-base neutralisation
  4. A physical change of state

Question 15

When does a cell made from two metals give a higher voltage?
  1. Further apart in reactivity
  2. Next to each other in reactivity
  3. Both equally unreactive
  4. Identical metals in identical conditions

Question 16

Why can a rechargeable battery be recharged?
  1. External current reverses the chemical reactions
  2. The current replaces both electrodes with new metals
  3. The current heats the cell until reactants return
  4. The original reaction restarts without restoring reactants

Question 17

In a hydrogen fuel cell, hydrogen reacts with oxygen to form?
  1. Water
  2. Hydrogen peroxide
  3. Carbon dioxide
  4. Methane

Question 18

What is one advantage of hydrogen fuel cells at point of use?
  1. It produces water rather than carbon dioxide
  2. It produces carbon dioxide rather than water
  3. It releases hydrogen as the main product
  4. It stores charge without a chemical reaction

Question 19

On reaction profiles, what sign is ΔH for exothermic reactions?
  1. Negative
  2. Positive
  3. Zero
  4. The same sign as activation energy

Question 20

Why can the same bond type have slightly different bond energies?
  1. Its surrounding atoms can differ
  2. Its atoms change their proton numbers
  3. Its colour changes the bond strength
  4. Its measuring unit changes between compounds

Question 21

Breaking bonds needs \(250\,\mathrm{kJ\,mol^{-1}}\); forming bonds releases \(400\,\mathrm{kJ\,mol^{-1}}\). What is \(\Delta H\)?
  1. \(-150\,\mathrm{kJ\,mol^{-1}}\)
  2. \(+150\,\mathrm{kJ\,mol^{-1}}\)
  3. \(-650\,\mathrm{kJ\,mol^{-1}}\)
  4. \(+650\,\mathrm{kJ\,mol^{-1}}\)

Question 22

Why is breaking bonds endothermic?
  1. Energy is required to overcome attractions
  2. Energy is released when attractions are overcome
  3. Atoms are destroyed
  4. Electrons are made

Question 23

What is a reaction profile?
  1. A graph of energy changes during a reaction
  2. A graph of mass against volume
  3. A table of element symbols
  4. A method of filtration

Question 24

Where are products shown on an endothermic reaction profile?
  1. Above the reactants
  2. Below the reactants
  3. Level with the reactants
  4. At zero energy

Question 25

What does a calorimeter measure in school experiments?
  1. Temperature change caused by a reaction
  2. Number of moles directly
  3. Mass of electrons
  4. pH

Question 26

A \(1\,\mathrm{kg}\) sample has \(c=500\,\mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}\). What energy raises it by \(2\,{}^\circ\mathrm{C}\)?
  1. \(1000\,\mathrm{J}\)
  2. \(250\,\mathrm{J}\)
  3. \(500\,\mathrm{J}\)
  4. \(1002\,\mathrm{J}\)

Question 27

How does a battery differ from a single electrochemical cell?
  1. It contains two or more cells
  2. It stores charge without chemical reactions
  3. It works only with alternating current
  4. It contains one electrode instead of two

Question 28

What does a larger potential difference in a cell indicate?
  1. A greater difference in energy between the reactions
  2. A lower energy difference between reactions
  3. A larger number of electrons in each atom
  4. A lower concentration of reactants

Question 29

Why can hydrogen fuel still have lifecycle carbon emissions?
  1. Producing the hydrogen may use fossil fuels
  2. Water from the fuel cell contains carbon
  3. Hydrogen atoms turn into carbon during storage
  4. Oxygen releases carbon dioxide when reduced

Question 30

What is a disadvantage of hydrogen fuel cells?
  1. Hydrogen production and storage can be difficult
  2. Hydrogen has a high energy per unit mass
  3. Water is produced at point of use
  4. A fuel cell can be refuelled quickly

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Review Energy changes questions for Chemistry, with correct answers shown and coverage across exothermic and endothermic reactions; reaction profile diagrams; activation energy.

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